Numerous biomedical applications require rapid and precise quantification of biological cells and/or molecules in a sample. One approach for performing such quantification is to employ magnetic probes which can bind to the species of interest and be captured by a magnet. For example, a wall of a device can contain a magnet, and species that have magnetic probes attached can be captured at the wall. However, such approaches can suffer from several shortcomings, such as large size, low capture rate, and cumbersome release methods.
For the specific case of biomolecules, a magnetic sifter approach was considered in US 2007/0181466, hereby incorporated by reference in its entirety. The magnetic sifter has pores that pass through a substrate such that a soft magnetic material is present near the pores. With this arrangement, magnetically labeled biomolecules can be captured at and released from the pores of the sifter by using an external magnetic field to alter the magnetic field produced by the soft magnetic material at the pores.
Controllably capturing and releasing biomolecules from the pores of a magnetic sifter is substantially easier than performing the same operation for biological cells, because molecules are smaller than cells and have more predictable behavior. Accordingly, it would be an advance in the art to provide capture and release of biological cells using a magnetic sifter.